VISIT REPORT
L. Burnard

ICL Computer House
Euston

21 June 79

ICL
DMUG EUFSG(79) no. 5

Some definite progress towards agreement
on what sort of conceptual view the projected end user facility should
support was made at this meeting, and not before time. There was
general agreement that entity modelling (as per ICL's Data Dictionary
System) was the most effective technique currently available for
mapping any end-user view onto whatever storage structures a
particular DBMS employed (i.e. IDMS structures in practise, though
theoretically any other DBMS could be used). Such techniques would
result however in a global data model inappropriate to all but a few
end-users. The group proposed that 'local' data models appropriate to
various categories of end user should be supported, the mapping from
each of these, via the global model, to the storage model to be the
responsibility of the EUF proper. Such local models would not
necessarily be simple subsets of the global model; in some cases
relationships present in the global model might be suppressed, in
others relationships not actually implemented in the storage model
(because of e.g. volumetric considerations) might be present. I
stressed the importance to University users of providing a relational
local model, with some grudging support. It seemed probable that the
DBS would/could be enhanced to provide support for local data models
in this way, especially since construction of a global model for the
DDS inevitably involved as a first step the construction of local
models. The DDS subgroup would investigate.